Deputy Prime Minister John Prescott has written to Labour MPs in an effort to head-off a backbench revolt over plans to partially privatise the air traffic control system.

The government is facing what could be its biggest backbench rebellion so far over its plans to privatise National Air Traffic Services (Nats).

MPs are being asked to support a rebel amendment to the government bill when it returns to the Commons on 9 May.

But Mr Prescott, who has responsibility for transport, says safety will not be undermined by the proposals to sell off a 51% stake in the service.

Any rebellion would embarrass the government, which has already seen revolts this session on its freedom of information bill, moves to limit jury trials and pensions.

Opposed in opposition

The privatisation of Nats was repeatedly opposed by Labour before the general election.

The main focus of the current opposition to the partial sell-off is the concern over safety.

John Prescott: Written to MPs

The Institution of Professionals, Managers and Specialists, which
represents 3,500 air traffic controllers, says the government has "failed to
address legitimate concerns about safety".

Last month, the government dismissed a Commons select committee report which claimed part-privatisation was the worst option for air traffic control services.

Former Labour transport minister Gavin Strang, who has been leading backbench opposition to the sell-off, has accused the government of not adequately addressing "real concerns on national security and passenger safety" raised by the scheme.

He said: "It is time the government listened to the concerns of pilots and
the general aviation sector. The dialogue between pilots and air traffic
controllers is crucial to air traffic management."

Nats, part of the Civil Aviation Authority, employs 5,000 people, including 1,700 controllers and 1,500 engineers and administrative staff.

It provides air traffic control at the UK's major airports and operates from two major centres, West Drayton, near Heathrow, which is due to be replaced by a £350m centre at Swanwick, Hampshire, and Prestwick, Ayrshire, where a new £250m centre is expected to open in 2002.

In March, Peter Reed, former manager of economic regulation at the Civil Aviation Authority which runs NATS, said: "This 'Railtrack in the sky' has no justification in economic, financial or operational terms."